Chemistry - Solid State Question with Solution | TestHub

In a face-centered cubic (fcc) crystal lattice, the coordination number is defined as the number of nearest neighbouring spheres for any given particle.

Considering a face-centered atom, it is in contact with $4$ corner atoms in its own plane. Additionally, it is in contact with $4$ face-centered atoms in the plane immediately above it and $4$ face-centered atoms in the plane immediately below it.

Total number of nearest neighbours $=4+4+4=12$.

Thus, the coordination number for any particle in an fcc lattice is $12$.

Answer: $12$